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Two new species of Marphysa Quatrefages, 1866 are described from the southeast coast of Australia. With the presence of only compound spinigers and the branchiae present over many chaetigers, Marphysa baudini n. sp. belongs to the Sanguinea-group. This species has ventral cirri with an inflated base and digitiform tip and thick and wide anodont pectinate chaetae, with 3–5 internal long and thick teeth. With the presence of only compound falcigers, Marphysa davidattenboroughi n. sp., belongs to the “Aenea-group”. This species is characterised by the presence of a bilobed prostomium, a single pair of pygidial cirri and by the presence of thick, and wide anodont pectinate chaetae with 4–6 long internal and thick teeth.

Trematodes are the main macroparasites in coastal waters. The most abundant and widespread form of these parasites is metacercaria. Their impact on their host fitness is considered relatively low but metacercarial larvae of some species can have deleterious effects on individuals and/or populations. This review focused on the cockle Cerastoderma edule and four species of the genus Himasthla; a common host–parasite system in marine coastal environments. Our aims were (1) to review literature concerning Himasthla continua, Himasthla elongata, Himasthla interrupta and Himasthla quissetensis in cockles; (2) to provide molecular signatures of these parasites and (3) to analyse infection patterns using a 20-year monthly database of cockle monitoring from Banc d'Arguin (France). Due to identification uncertainties, the analysis of the database was restricted to H. interrupta and H. quissetensis, and it was revealed that these parasites infect cockles of the same size range. The intensity of parasites increased with cockle size/age. During the colder months, the mean parasite intensity of a cockle cohort decreased, while infection occurred in the warmest season. No inter-specific competition between trematode parasites was detected. Furthermore, even if the intensity of H. interrupta or H. quissetensis infection fluctuated in different years, this did not modify the trematode community structure in the cockles. The intensity of infection of both species was also positively correlated with trematode species richness and metacercarial abundance. This study highlighted the possible detrimental role of Himasthla spp. in cockle population dynamics. It also revealed the risks of misidentification, which should be resolved by further molecular approaches.

The amphipod Ericthonius didymus Krapp-Schickel, 2013 is reported for the first time outside its type locality in European waters, from the French Atlantic coast and from the Azores, Portugal. In particular, a large population was recorded in Arcachon, France. Molecular analyses were made to confirm the validity of three closely related Ericthonius species: E. didymus, E. convexus and E. pugnax. An identification key is provided, distinguishing Ericthonius species into three groups, based on the presence or absence of stridulating ridges on coxa 2 and posterodistal lobe on basis of male pereopod 5.

The most deleterious stage of a trematode life cycle occurs in the first intermediate host where the parasite penetrates as a miracidium and asexually multiplicates in sporocysts or rediae. When infection advances, other organs can be occupied with severe effects on host individual health and population dynamics. Existing studies focused on these host/parasite systems are still scarce due to the usual low prevalence in ecosystems. Using cockles (Cerastoderma spp.) and two trematode species (Monorchis parvus and Gymnophallus choledochus) infecting these bivalves as first and second intermediate host, the present work aimed to (1) summarize the most relevant literature and (2) provide new information regarding this host/parasite system, taking advantage of a 21-year monthly database from Banc d'Arguin (France). This long-term monitoring showed that different trematode species display varying host size range preference (6–38 and 31–36 mm for M. parvus and G. choledochus, respectively). The occurrence of coinfection was lower than expected, raising some questions related to parasite interspecific competition. This review improved our understanding of the processes shaping the prevalence and distribution of parasitism. This study highlighted that beyond constant trematode assemblage monitoring, there is a need to identify the main predictors of rediae/sporocysts infection, such as the definitive host dynamics and miracidium infection processes, for future better management of host severe disease and mortality episodes.

Despite still being a matter of debate, there is growing evidence that pollutant-induced epigenetic changes can be propagated across generations. Whereas such modifications could have long-lasting effects on organisms and even on population, environmentally relevant data from long-term exposure combined with follow-up through multiple generations remain scarce for non-mammalian species. We performed a transgenerational experiment comprising four successive generations of zebrafish. Only fish from the first generation were exposed to an environmentally realistic concentration of cadmium (Cd). Using a whole methylome analysis, we first identified the DNA regions that were differentially methylated in response to Cd exposure and common to fish of the first two generations. Among them, we then focused our investigations on the exon 3 (ex3) of the cep19 gene. We indeed recorded transgenerational growth disorders in Cd-exposed fish, and a mutation in this exon is known to cause morbid obesity in mammals. Its methylation level was thus determined in zebrafish from all the four generations by means of a targeted and base resolution method. We observed a transgenerational inheritance of Cd-induced DNA methylation changes up to the fourth generation. However, these changes were closely associated with genetic variations, mainly a single nucleotide polymorphism. This single nucleotide polymorphism was itself at the origin of the creation or deletion of a methylation site and deeply impacted the methylation level of neighboring methylation sites. Cd-induced epigenetic changes were associated with different mRNA transcripts and an improved condition of Cd fish. Our results emphasize a tight relationship between genetic and epigenetic mechanisms and suggest that their interplay and pre-existing diversity can allow rapid adaptation to anthropogenic environmental changes.

This work is the last of four papers of the Spaghetti Project, aiming to revise the species of terebellids, a.k.a. “spaghetti” worms, present in the European French waters. In this last paper the Terebellidae, sensu stricto, from French waters are revised based, on material available in the French marine stations, type materials stored in the MNHN collection and newly collected specimens. Nine new species are described using both morphological and molecular tools: Eupolymnia gili n. sp., E. lacazei n. sp., E. meissnerae n. sp., Lanice kellyslateri n. sp., Paramphitrite dragovabeci n. sp., Pista labruneae n. sp., P. miosseci n. sp., P. sauriaui n. sp., and Terebella banksyi n. sp. European species of Eupolymnia are distinguished mainly by the shape of the lateral lobes and the size of the branchial stems. The two species belonging to Lanice genus are distinguished by the fusion of the first ventral shields, the shape of both noto- and neuropodia, and the pigmentation of the upper lip. The two species of Paramphitrite are distinguished by the presence or absence of a medial dorsal gap between the pairs of branchiae, by the shape of the lateral lobes and the presence or absence of a nephridial papilla on segment 4. The different species of Pista are distinguished by the number of pairs of branchiae, the shape of the lateral lobes and uncini. Finally, the two species of Terebella are distinguished by the number of segments with nephridial and genital papillae and the segments on which the branchiae occur. An identification key for European species of Terebellidae sensu stricto is also provided.

We report the mitochondrial genome of Sabella spallanzanii, an invasive Mediterranean sabellid introduced to Australia and New Zealand. The mitogenome is 15,581 bp long and consists of 38 genes, including 13 protein coding genes, two rRNA genes, and 23 tRNA genes. It shows deviations from the putative annelid ground pattern, such as gene order re-arrangements and regions encoding on the negative strand. It is, however, very different from the mitogenome of the closely related serpulid, Spirobranchus giganteus. Phylogenetic analyses of the mitochondrial genes support a sister relationship of Sabella spallanzanii and Spirobranchus giganteus.

The European sturgeon, Acipenser sturio, is a highly endangered species that almost disappeared in the last decades. Thanks to yearly restocking of the population, this species is still found in the Gironde estuary (France), where juveniles grow during several years before leaving to the ocean. The aims of this study were to evaluate the pressure exerted on these fish by known organic and inorganic contaminants during their stay at the Gironde estuary, and to get information on the fish’s health in this context. Monthly captures over the year 2014 provided 87 fish from the cohorts 2012 and 2013 mainly, and from cohorts 2008, 2009, and 2011, all fish born in hatchery. We report the very first analyses of contaminant levels and of biological markers measured in the blood of these fish. Low inorganic contamination was found, composed of seven metals mainly Zn (

International audience; New Caledonia is particularly affected by nickel open pit mining activities because of the presence of ultramafic soils rich in metal trace elements. The nickel particles dispersed by atmospheric transport and soil erosion during the excavation of nickel will end up by deposition or leaching in aquatic ecosystems where they may be bioaccumulated by living organisms in the rivers downstream the mines. Despite alarming freshwater metals concentrations, no study investigated the level of their bioaccumulation in eels living downstream mining sites, and if high bioaccumulation levels occur, the potential consequences on eel's health. The aim of this study was to determine how eels Anguilla marmorata are impacted in situ by metal concentrations issued from mining activity by measuring: morphometric parameters; metal concentrations in tissues and organs and transcription levels of target genes encoding proteins involved in several metabolic key functions. Among organs, liver was found to be the most affected by mining with average nickel concentrations of 5.14 mg/kg versus 1.63 mg/kg for eel liver away from mines leading to dysregulation of numerous genes involved in oxidative stress, DNA repair, apoptosis, reproduction and both lipid and mitochondrial metabolisms. This study should allow us to define in an integrated way if metals released by mining activities influence metals bioaccumulation in eels and induce biological effects.

International audience; Sex determination is a complex process that can be influenced by environment in various taxa. Disturbed environments can affect population sex ratios and thus threaten their viability. Emerging evidences support a role of epigenetic mechanisms, notably DNA methylation, in environmental sex determination (ESD). In this work, using zebrafish as model and a transgenerational experiment comprising 4 successive generations, we report a strength link between the promotor methylation level of three genes in female gonads and population sex ratio. One generation of zebrafish was exposed throughout its lifetime to cadmium (Cd), a non-essential metal, at an environmentally relevant concentration. The subsequent generations were not exposed. At the first and the third generation a subset of individuals was exposed to an elevated temperature, a well-known masculinizing factor in zebrafish. While heat was associated to an increase in the methylation level of cyp19a1a gene and population masculinization, foxl2a/dmrt1 methylation levels appeared to be influenced by Cd and fish density leading to offspring feminization. Ancestral Cd exposure indeed led to a progressive feminization of the population over generations and affected the sex plastic response of zebrafish in response to heat. The effect of Cd on the methylation level of foxl2a was observed until the third generation, supporting potential transgenerational inheritance. Our results support (i) a key role of cyp19a1a methylation in SD in zebrafish in response to environmental cues and (ii) the fact that the environment experienced by parents, namely mothers in the present case, can affect their offspring sex ratio via environment-induced DNA methylation changes in gonads.

International audience; Polycirridae from French waters are revised based on material available in French marine stations and newly collected specimens. This work is the third part of the Spaghetti Project aiming to revise French species of "Spaghetti" terebellid worms. It describes eight new species using both morphological (for all species) and molecular (for some species) tools: Amaeana gremarei n. sp., Polycirrus catalanensis n. sp., P glasbyi n. sp., P gujanensis n. sp., P idex n. sp., P. nogueirai n. sp., P. pennarbedae n. sp. and P readi n. sp., in addition to a previously described species. An identification key for European species of Polycirridae is also provided.

A new species of Marphysa is described from India using both morphology and molecular data. The new species, Marphysa madrasi, belonging to the Teretiuscula-group, is characterised by having antennae about 2x longer than the prostomium, maxillae II and IV with a relatively large number of teeth (Mx II with 8+9; Mx IV with 7+11), compound spinigers present on a large range of mid-body chaetigers (at least 83–159), and pectinate chaetae present from the first few anterior chaetigers. We discuss all the species of this genus lacking compound falcigers (i.e., those belonging to the Sanguinea-, Mossambica- and Teretiuscula-groups), which have been reported from India and compare them to our new species. Only two accepted species in these groups can be confirmed as occurring in India, M. madrasi n. sp. and M. gravelyi Southern, 1921. We provide a table that summarises the important characters useful to identify species in this group of Marphysa with compound spinigers.

Telothelepodidae and Thelepodidae from French waters are revised based on material available in French marine stations and newly collected specimens. This work is the second part of the Spaghetti Project aiming to revise French species of “Spaghetti” worms. It describes three new species using both morphological and molecular tools: Streblosoma cabiochi n. sp., Streblosoma lindsayae n. sp. and Thelepus corsicanus n. sp. This study also permitted us to detect the presence of an Asiatic species, Thelepus japonicus, in Arcachon Bay and Normandy, introduced via oysters transfers. An identification key for European species of both families is also provided.

Dwarf eelgrasses (Zostera noltei) populations have decreased since 2005 in Arcachon Bay (southwest France). Various stressors have been pointed out, however the role of xenobiotics like pesticides or copper (Cu) and of parameters like water temperature warming have not yet been explored. To determine their impact, Z. noltei individuals were collected in a pollution-free site and transferred to the laboratory in seawater microcosms. This dwarf eelgrass was exposed to a pesticide cocktail and copper, alone or simultaneously, at temperatures (10 °C, 20 °C, 28 °C) representative of different seasons. After a two-week contamination, leaf growth, leaf bioaccumulation of Cu, and differential expression of target genes were studied. Eelgrasses bioaccumulated Cu regardless of the temperature, with reduced efficiency in the presence of the Cu and pesticide cocktail at the two higher temperatures. High temperature also exacerbated the effect of contaminants, leading to growth inhibition and differential gene expression. Mitochondrial activity was strongly impacted and higher mortality rates occurred. Experimental results have been confirmed during field survey. This is the first report on the impacts on Z. noltei of pesticides and Cu associate to temperature.

Marine sediments are an important source of contaminants since they are susceptible to be remobilized to the water column. By modifying the physical and biogeochemical characteristics of sediments, bioturbation can influence contaminants remobilization. Within bioturbators, mud shrimp are considered as among the most influential organisms in marine soft-bottom environments. The physiological state of mud shrimp can be impaired by bopyrid parasites. The present study aims to evaluate the influence of bopyrid-uninfested and bopyrid-infested mud shrimp on sediment contaminants resuspension. Through a 14-days ex-situ experiment we showed a moderate effect of mud shrimp on contaminant remobilization compared to molecular diffusion without the bioturbator. Conversely, parasite presence significantly impaired contaminant bioaccumulation in mud shrimp and interfered with genetic expression. The weak effect of mud shrimp on contaminant remobilization may be due to trace metal accumulation and thus we suggested to evaluate the influence of contaminants on activities of bioturbating species.

Mitochondrial genomes are frequently applied in phylogenetic and evolutionary studies across metazoans, yet they are still poorly represented in many groups of invertebrates, including annelids. Here, we report ten mitochondrial genomes from the annelid genus Hydroides (Serpulidae) and compare them with all available annelid mitogenomes. We detected all 13 protein coding genes in Hydroides spp., including the atp8 which was reported as a missing gene in the Christmas Tree worm Spirobranchus giganteus, another annelid of the family Serpulidae. All available mitochondrial genomes of Hydroides show a highly positive GC skew combined with a highly negative AT skew – a feature consistent with that found only in the mitogenome of S. giganteus. In addition, amino acid sequences of the 13 protein-coding genes showed a high genetic distance between the Hydroides clade and S. giganteus, suggesting a fast rate of mitochondrial sequence evolution in Serpulidae. The gene order of protein-coding genes within Hydroides exhibited extensive rearrangements at species level, and were different from the arrangement patterns of other annelids, including S. giganteus. Phylogenetic analyses based on protein-coding genes recovered Hydroides as a monophyletic group sister to Spirobranchus with a long branch, and sister to the fan worm Sabellidae. Yet the Serpulidae + Sabellidae clade was unexpectedly grouped with Sipuncula, suggesting that mitochondrial genomes alone are insufficient to resolve the phylogenetic position of Serpulidae within Annelida due to its high base substitution rates. Overall, our study revealed a high variability in the gene order arrangement of mitochondrial genomes within Serpulidae, provided evidence to question the conserved pattern of the mitochondrial gene order in Annelida and called for caution when applying mitochondrial genes to infer their phylogenetic relationships., The study was mainly funded by Australian Biological Resources Study (ABRS) grants RF213-19 and RG18–21 to EKK and an International Macquarie University Research Excellence Scholarship (iMQRES) from Macquarie University to YS. The data analysis and paper writing were partly supported by Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (GML2019ZD0404, GML2019ZD0409, L20190005) to JWQ and by French State in the frame of the “Investments for the future” Programme IdEx Bordeaux (ANR-10-IDEX-03-02) to GD.

The wedge clam (Donax trunculus) is widely distributed along exposed Atlantic coasts, from France to Senegal. This species has high commercial importance, with the mean capture production on the last ten years of approx. 850 tonnes (50% represented by Portugal captures). D. trunculus populations are modulated by several drivers such as tidal range, temperature, sediment grain size, fishing pressure, predation and parasitism. Regarding parasitism, D. trunculus is the first intermediate host of Bacciger bacciger (trematode parasite) where the sporocysts develop. The sporocyst is the most damaging stage, reported as being responsible for bivalve castration and flesh mass depletion. In order to test the hypothesis that B. bacciger infection modified wedge clam health status, including its biochemical performance and gene expression, clams were sampled every other month during one year in the Faro beach (south coast of Portugal). The results obtained revealed that B. bacciger total prevalence ranged between 0 and 33% in May and July, respectively. Overall, transcriptomic and biochemical results showed that B. bacciger induced in D. trunculus defense mechanisms against oxidative stress and increased the host metabolism and energy demand, especially in spawning and spent periods. The present work concluded that the markers used can provide additional and ecologically relevant information not only about the environmental conditions that animals experience but also the invasion effects of pathogens. These findings can contribute to predicting organism chance of reproduction and survival in their natural context, which can be applied in bivalve conservation and disease episodes management. National Funds through the Portuguese Foundation for Science and Technology - FSE [PD/BD/52570/2014] Programa Operacional Capital Humano (POCH) European UnionEuropean Union (EU) INTERREG-ATLANTIC program through the research project COCKLES [EAPA_458/2016 COCKLES] Integrated Programme of SR&TD "Smart Valorization of Endogenous Marine Biological Resources Under a Changing Climate" - Centro 2020 program, Portugal 2020, European Union, through the European Regional Development Fund [Centro-01-0145-FEDER-000018] FCT/MEC, through national funds FEDER, within the PT2020 Partnership Agreement Compete 2020

International audience; Understanding how organisms cope with global change is a major question in many fields of biology. Mainly, understanding the molecular mechanisms supporting rapid phenotypic changes of organisms in response to stress and linking stress-induced molecular events to adaptive or adverse outcomes at the individual or population levels remain a major challenge in evolutionary biology, ecology or ecotoxicology. In this view, the present study aimed to test (i) whether environmental factors, especially pollutants, can trigger changes in the activity of retrotransposons (RTs) in wild fish and (ii) if changes in RT DNA methylation or transcription levels can be linked to modifications at the individual level. RTs are genetic elements that have the ability to replicate and integrate elsewhere in the genome. Although RTs are mainly quiescent during normal development, they can be experimentally activated under life-threatening conditions, affecting the fitness of their host. Wild eels were collected in four sampling sites presenting differing levels of contamination. The methylation level and the transcriptional activity of two RTs and two genes involved in development and cell differentiation were analyzed in fish liver in addition to the determination of fish contaminants levels and diverse growth and morphometric indices. An up-regulation of RTs associated to lower methylation levels and lower growth indices were observed in highly contaminated fish. Our results suggest that RT activation in fish experiencing stress conditions could have both detrimental and beneficial implications, affecting fish growth but promoting resistance to environmental stressors such as pollutants. Retrotransposons could represent interesting environment-sensitive molecular markers allowing to link stress-induced molecular events to adverse outcomes at higher levels.

The worldwide increase of graphene family materials raises the question of the potential consequences resulting from their release in the environment and future consequences on ecosystem health, especially in the aquatic environment in which they are likely to accumulate. Thus, there is a need to evaluate the biological and ecological risk but also to find innovative solutions leading to the production of safer materials. This work focuses on the evaluation of functional group-safety relationships regarding to graphene oxide (GO) in vivo genotoxic potential toward X. laevis tadpoles. For this purpose, thermal treatments in H2 atmosphere were applied to produce reduced graphene oxide (rGOs) with different surface group compositions. Analysis performed indicated that GO induced disturbances in erythrocyte cell cycle leading to accumulation of cells in G0/G1 phase. Significant genotoxicity due to oxidative stress was observed in larvae exposed to low GO concentration (0.1 mg·L−1). Reduction of GO at 200 °C and 1000 °C produced a material that was no longer genotoxic at low concentrations. X-ray photoelectron spectroscopy (XPS) analysis indicated that epoxide groups may constitute a good candidate to explain the genotoxic potential of the most oxidized form of the material. Thermal reduction of GO may constitute an appropriate “safer-by-design„ strategy for the development of a safer material for environment.

The common bait wormMarphysasanguinea(Montagu, 1813), originally described from the south coast of England, is the type species of the genus. This species has been widely reported from all around the world and has been considered as cosmopolitan until recently. This is partly because the original description was very brief and poorly illustrated, and also because all species superficially look similar. In order to clarify the situation,M.sanguineawas redescribed and a neotype was designated by Hutchings and Karageorgpoulos in 2003. Recently, specimens from Cornwall, close to the type locality, were sampled, examined morphologically, and used to obtain COI gene sequences for this species. Molecular results permitted us to confirm the identity and presence ofM.sanguineaalong the French coasts and to highlight the presence of inaccurate sequences of this species on GenBank. Use of this “false” cosmopolitan species at a worldwide scale by many biologists is also discussed in this paper.

A new species of Eunicidae, Marphysa victori sp. n., has been identified from Arcachon Bay, Bay of Biscay, NE Atlantic. This new species, belonging to the sanguinea complex, is characterised by branchiae with long filaments from chaetigers 26–34, the presence of four types of pectinate chaetae with first ones present from chaetiger 2, a large number of both pectinate chaetae and compound spinigers, and the pygidium with only one pair of pygidial cirri. An identification key for European species of the genus Marphysa is provided.

The mud shrimp Upogebia pusilla is a deep-burrowing bioturbator widespread along the Northeast Atlantic and Mediterranean coasts, where it is recognized as an ecosystem engineer. Parasitism is an important factor impacting such species’ activities, and thus ecosystem functioning. At least two parasite species occur in U. pusilla: the bopyrid isopod Gyge branchialis and an undescribed trematode. This study, carried out in Arcachon Bay, France (44°40′N, 1°10′W), over 2 years (2014–2015), had two goals: (1) to identify the trematode occurring in U. pusilla and (2) to assess the interactions between the two parasites within their host. Using molecular techniques, the trematode was identified as Maritrema sp. (Microphallidae). Monthly samples taken over 2 years at a single site, and a ten-site spatial survey in June 2014 showed that there was a negative association in the occurrence of the two parasites in their host over time and amongst sites: bopyrid-infested mud shrimp harbored lower trematode infections compared to bopyrid-free individuals. In addition, the abundance of trematodes was lower in the bopyrid-infested gill compared to the uninfested gill of bopyrid-infested individuals. It suggests that G. branchialis interferes with Maritrema sp. establishment in the mud shrimp. Conversely, the trematode appeared not to have a negative effect on bopyrid presence. The reduction of Maritrema sp. infection by G. branchialis is mainly due to the alteration of U. pusilla fitness (indirect interaction), and to a lesser extent, to overlap of parasites’ niches (direct interaction). Accordingly, interactions between these two parasites can be classified as amensalism.

This paper describes the development of an integrative embryo-toxicity assay in Japanese medaka allowing analysis of several toxicological endpoints together in a same individual. In this assay, embryos are topically exposed, and survival, hatching success, malformations, biometry, behaviour, and target gene expression are subsequently analysed in each individual. This assay was applied to oxazepam, an anxiolytic pharmaceutical compound currently found in wastewater treatment plant effluent. Even if oxazepam accumulation in embryos was very low, it caused spinal and cardiac malformations, delayed growth, erratic swimming and deregulation of genes involved in apoptosis, DNA repair and mitochondrial metabolism. Relationship between gene deregulation, abnormal behaviour, and developmental anomalies was demonstrated. This assay is sensitive enough to detect adverse effects at low chemical concentrations and at multiple endpoints in a unique fish embryo. This integrative embryo-toxicity assay is a powerful tool to characterize the spectrum of effects of new chemicals and also to link effects induced at different molecular, tissue and physiological levels.

The Riou-Mort watershed (southwest France) exhibits high metal contaminations (Cd and Zn) related to an important mining past. In this context, a remediation process has been implemented in 2007 to reduce the watershed contamination. The aim of this study was to assess the early effectiveness of the remediation process on the hydrosystem contamination state. A biomonitoring was realized over two years (2008-2010) with the filter-feeding bivalve Corbicula fluminea, exposed along a contamination gradient. Several biological parameters were monitored: (1) Cd and Zn bioaccumulation, (2) Metallothionein (MT) production as detoxification mechanism, (3) differential gene expression (cat, sod, gst, 12S, cox1, mt). The physicochemical data highlighted strong metal contamination persistence in the river water and failed to demonstrate a significant decrease of metal contamination during the 2-year monitoring. The bioaccumulation results confirmed the persistence of a water contamination despite remediation works, with maximum values measured downstream from the industrial site (Joany). The bioaccumulation increased in 2010, reaching 69.3±5.3 μg Cd g(-1) DW at Joany in July 2010, whereas it did not exceed 1.4±0.2 μg Cd g(-1) DW at the reference site throughout the biomonitoring. MT concentrations were closely related to the contamination gradient, especially at Joany, demonstrating their strong involvement in the detoxification processes. The mt gene induction was strongly correlated to the MT and metal concentrations. The gene inductions of cat, sod, gst and 12S were correlated to both the metal concentrations and the seasonal variations, especially temperatures. This suggests that environmental factors require serious consideration for the interpretation of bioaccumulation kinetics and thus for the assessment of the remediation effectiveness. Consequently, the whole results did not yet highlight strong beneficial effects of remediation work on the hydrosystem contamination state. First benefits of that process should be progressively felt, once the remediation achieved, and should grandly accelerate the decontamination process of the contaminated area.

Bivalve populations are controlled by several biotic and abiotic factors. Parasitism is among the biotic factors but is often neglected. In the present study, we focused on the transcriptomic and biochemical responses of Cerastoderma edule when parasitized as first intermediate host by the trematode Bucephalus minimus (sporocyst, the most damaging stage), and taking into account seasonal patterns. In order to test the hypothesis that the presence of B. minimus compromises cockle regular gene expression and biochemical performance and increases their vulnerability to other parasite species infection, cockles were sampled every other month during one year in Arcachon Bay (French Atlantic coast). Overall, results showed that B. minimus induced its first intermediate host defence mechanism against oxidative stress (mainly at gene level), increased host metabolism and energy demand especially in summer (revealed at both gene and biochemical level, although without significant differences) and was accompanied by a higher metacercariae abundance. Results allowed to accept the posted hypothesis and to conclude that transcriptomic and biochemical markers can provide additional and ecologically relevant information about parasite effects on their hosts, reflecting the invasion effects of pathogens but also the environmental conditions that animals experience.

00000; International audience; Asari (= Manila) clam, Ruditapes philippinarum, is the second bivalve mollusc in terms of production in the world and, in many coastal areas, can beget important socio-economic issues. In Europe, this species was introduced after 1973. In Arcachon Bay, after a decade of aquaculture attempt, Asari clam rapidly constituted neo-naturalized population which is now fished. However, recent studies emphasized the decline of population and individual performances. In the framework of a national project (REPAMEP), some elements of fitness, stressors and responses in Arcachon bay were measured and compared to international data (41 publications, 9 countries). The condition index (CI=flesh weight/shell weight) was the lowest among all compared sites. Variation in average Chla concentration explained 30% of variation of CI among different areas. Among potential diseases, perkinsosis was particularly prevalent in Arcachon Bay, with high abundance, and Asari clams underwent Brown Muscle Disease, a pathology strictly restricted to this lagoon. Overall element contamination was relatively low, although arsenic, cobalt, nickel and chromium displayed higher values than in other ecosystems where Asari clam is exploited. Finally, total hemocyte count (THC) of Asari clam in Arcachon Bay, related to the immune system activity, exhibited values that were also under what is generally observed elsewhere. In conclusion, this study, with all reserves due to heterogeneity of available data, suggest that the particularly low fitness of Asari clam in Arcachon Bay is due to poor trophic condition, high prevalence and intensity of a disease (perkinsosis), moderate inorganic contamination, and poor efficiency of the immune system.

International audience; There is increasing evidence that pollutants may cause diseases via epigenetic modifications. Epigenetic mechanisms such as DNA methylation participate in the regulation of gene transcription. Surprisingly, epigenetics research is still limited in ecotoxicology. In this study, we investigated whether chronic exposure to contaminants experienced by wild female fish (Anguilla anguilla) throughout their juvenile phase can affect the DNA methylation status of their oocytes during gonad maturation. Thus, fish were sampled in two locations presenting a low or a high contamination level. Then, fish were transferred to the laboratory and artificially matured. Before hormonal treatment, the DNA methylation levels of the genes encoding for the aromatase and the receptor of the follicle stimulating hormone were higher in contaminated fish than in fish from the clean site. For the hormone receptor, this hypermethylation was positively correlated with the contamination level of fish and was associated with a decrease in its transcription level. In addition, whereas gonad growth was associated with an increase in DNA methylation in fish from the clean site, no changes were observed in contaminated fish in response to hormonal treatment. Finally, a higher gonad growth was observed in fish from the reference site in comparison to contaminated fish.

This study aimed to assess the recovery capacity of the freshwater bivalve Corbicula fluminea subjected to industrial metal discharges (Cd, Zn). After a 24-day exposure in a metal-contaminated river, bivalves were transferred and maintained in the laboratory for one year under metal-free conditions. Metal accumulation, metallothionein production and genetic expressions of genes involved in metal stress were studied. Results demonstrated the high persistence of Cd in tissues (only 73% eliminated after 365 days) whereas Zn was rapidly depurated. The Cd half-life was estimated around 240 days. Metallothioneins were strongly induced within the 28 first days of decontamination, then decreased by 45% after 365 days. The metal exposure of bivalves led to a significant gene induction. After 28 days, most of the genes were no longer overexpressed, suggesting that the bivalves may withstand small amounts of non-essential metals in their tissues without showing signs of detrimental effects on the tested genes.

This study was undertaken to develop molecular tools to assess water quality using diatoms as the biological model. Molecular approaches were designed following the development of a rapid and easy RNA extraction method suited to diatoms and the sequencing of genes involved in mitochondrial and photosystem metabolism. Secondly the impact of cadmium was evaluated at the genetic level by q-PCR on 9 genes of interest after exposure of Eolimna minima diatom populations cultured in suspension under controlled laboratory conditions. Their growth kinetics and Cd bioaccumulation were followed. Population growth rates revealed the high impact of Cd at 100 μg/L with total inhibition of growth. These results are linked to the high bioaccumulation values calculated after 14 days of exposure, 57.0 ± 6.3 μg Cd/g dw and 734.1 ± 70 μg Cd/g dw for exposures of 10 and 100 μg Cd/L respectively. Genetic responses revealed the impact of Cd on the mitochondrial metabolism and the chloroplast photosystem of E. minima exposed to 10 and 100 μg Cd/L with induction of cox1, 12S, d1 and psaA after 7 days of exposure for the concentration of 100 μg Cd/L and of nad5, d1 and psaA after 14 days of exposure for both conditions. This is the first reported use of q-PCR for the assessment of toxic pollution on benthic river diatoms. The results obtained presage interesting perspectives, but the techniques developed need to be optimized before the design of new water quality diagnosis tools for use on natural biofilms.